Turbine lubrication



Patented Oct. 25, 19 38 UNITED STATES PATENT, OFFICE mama LUBRICATION NoDrawing. Application April 24, 1937,

Serial No. 138,859

16 Claims.

This invention relates to improvements in turbine lubrication, and itcomprises improved methods of lubricating turbines and the like withmineral-oils and mineral oil compositions, known as turbine oils,wherein a small amount of a nitrophenyl alkyl thioether is maintained inthe circulating turbine oil to mitigate or substantially retard thenormal deterioration of the turbine oil occasioned by the operatingcondi- 10 tions under which lubrication is efiected, such as heat,moisture, aeration, etc.; and it also comprises improved turbine oilscontaining small amounts of an alkyl thioether ofa nitrobenzene, theimproved turbine oil being directly useful in lubricating turbines andthe like, and useful as make-up oil in the lubricating systems of suchmachines; all as more fully hereinafter set forth and as claimed.

In lubricating turbines and the like, the requirements for satisfactoryand safe lubrication are rather exacting. The modern steam turbines andthe like are relatively large and complicated machines which operate athigh speeds, and in which the rotating mechanism is delicately balanced.In commercial plants, these turbines are used for the-continuousdevelopment of large amounts of power, and it is essential that thelubrication system be entirely safe; that is, continuelly remainoperative, as well as be satisfactory from the standpoint of preventingundue wear upon the bearings and other moving parts.

In the usual lubricating system of such niachines, the turbine oil iscirculated under pressure from an oil reservoir through the variousparts of the machine, such as bearings, gears,

etc. Pressure is used to insure a positive feed or circulation oi theoil. After passing through the parts of the turbinebeing lubricated, theoil is then cooled and collected in a separating reservoir 40 or sump.In lubricating turbines, the oil is repeatedly re-cycled, and it is moreor less purified before being returned to the oil reservoir .containingthe feed oil.

In the sump, the cooled oil is maintained more or less at rest to permitthe separation or settling of the oil from other contamina bodies;

that is, the various impurities pi up by the oil during its-passagethroimhtheturbine parts being lubricated. Also the oil is irecuentlyflitered, centrifuged, or treated in other ways to .necessary inrecycling, in addition tothat reuntil clear oil flushes the bottom ofthe sump. 1o

The lace is a water-oil emulsion and contains a substantial amount ofoil; In this separation,- which is standard in turbine lubricatingsystems, there is a substantial loss of undeteriorated oil. Thussubstantial quantities of make-up oil are quired to replace thedeteriorated oil. Therefore, the consumption of oil is substantial,although the bulk of it is recycled.

Generally, the solid impurities such as dirt, metal particles, otherhard matter, etc., are present in the cooled oil in only relativelysmall amounts; and they may be termed foreign impurities, asdistinguished from the contaminating bodies which are more or lessinherent in the used lubricant, such as oil deterioration products andwater. If the cooled oil were dry, the foreign solid impurities might bereadily and completely separated by straining, settling, filtering, etc.But the presence of the water and other liquid or soft impurities,render it cult to obtain quick and complete tion or the good oil fromthe various impurities.

In circulating through the turbine, the oil becomes more or less wetted.During the passage of the oil through the entire circulating system, itpicks up more or less water, air,'solid particles and other impurities.In passing through the 7 main bearings, the oil becomes intimatelychurned together with the water and these for- 40 eign matters. Owing tothe higher temperature and the great surface speed of the'revolvingshaft, the foreign matter and part of the oil form emulsions, and theoil gradually breaks down. The other impurities, whether in solution orin sus- *5 pension, increase the eifect oi the v intheoiltends topromote such an The formation andoi'oildeterlmtionmoductsisindicatedby'an in in the acidity of the oil 50 products.

and the appearance of sludge. When the deterioration has proceeded to adangerous point, appreciable amounts of insoluble sludge separate fromthe oil. Prior to that time, intermediate deterioration products mayremain, dissolved or colloidally suspended in the oil. Such intermediateproducts tend to increase and stabilize the water-oil emulsion or "laceand render it dimcult to obtain a quick, clean stratification either inthe sump or during a later centrifuging to obtain an oil free ofdispersed water. trifuging, the separated oil might be ted to evaporateofi any residual" water, and this is sometimes done. But this is notalways advantageous or satisfactory. For one thing the heated oil has tobe again cooled before it can be fed into the turbine. This increasesthe expense. Second, although the water might be evaporated, the solubleoil deterioration products remain in solu-' tion; and they, by gradualaccumulation, render the oil more susceptible to absorb water and to'emulsification.

Thus in lubricating turbines, something more is required than to simplysupply the turbine with an oil which has the necessary lubricatingqualities. A prime requisite of safe turbine oil is that it be capableof relatively sharp stratification or separation from the moisture.etc., in the sump and centrifuge. Thus the emulsibility of turbine oilswith water, aqueous solutions and steam are important factors with thistype of lubricant.

Further, a satisfactory turbine oil must be sub:- stantially free ofingredients which readily deteriorate to form acids oremulsion-promoting rather strict set of specifications. turbine oils arelow-viscosity neutral oils. The

following table indicates the general range of their primary physicalcharacteristics: Gravity: "Arr. 24.5- 33.0 Viscosity, SUV: F -650 Flash,00: F 390 500v Color, NPA

might induce emulsification or sludge. The lowviscosity neutral oil soobtained must comply, within certain limits, with certain standardemulsion tests. emulsion test (ASTM D 157-36), wherein the time requiredfor the separation of a definite volume of oil from a. definite volumeof condensed steam, measured in seconds, is known as the SE number". Anacceptable turbine 011 should have an SE number not greater than '75.When the oil being recycled in the turbine shows an- SE number greaterthan 400, the circulating oil contains such amount of deteriorationproducts that it should be thoroughly purified and revitalized by theaddition of substantial amounts of make-up oil, it the entire amount isnot withdrawn and replenished.

Another important test is the test foracidity,

where the neutralization number is above 1.0,

the oil shouldbe discarded or reworked.

After cen- Turbine oils must comply with 8.. Generally One of thesetests is the Steam We have now' found that by incorporating a moderateamount of nitro-phenyl alkyl thioethers into the turbine oil, we obtainbetter lubrication and a greater stabilization of the oil. j Thenitrophenyl alkyl thioethers may be introduced into the circulatingturbine oil, either as it is being fed to the turbine, or during thecollecting and purifying of the oil; for ,instance, added in the sump.However, it is advantageous to incorporate this improvement agent withthe turbine oil prior to introducing it into the supply reservoir. Theturbine oils containing 0.1 to 1.0 percent of an ortho-nitro-phenylalkyl thioether disso'lved therein are superior lubricants for themodern turbine, and they may be recycled repeatedly, with intermediateseparation of water and other impurities, for' longer periods of time;the life of the lubricant being markedly increased by the presence ofthe' said thioethers. That is, in the present methods of improving thelubri cation of turbines, we maintain in the circulating oil asuflicient amount of the said nitro ethers to stabilize the oil and tofacilitate the stratification from water and other impurities during thepurification.

The nitro-phenyl alkyl thioether compounds here useful forv improvingturbine oils may be represented by the following formula:

invention. However, in some instances, we em ploy the 2:4-dinitro-phenylallrylv thioether All of these nitro-phenyl thioethers are soluble inmineral oils and various organic solvents. They are insoluble andimmiscible with water and aqueous liquids.- They are substantiallynonacid and do not readily develop acidity in contact with oil or water.They are excellent im provement agents for turbine oils.

These nitro-phenyl alkyl thioethers may be obtained by condensing anitro-chlorobenzene in alcoholic solution with various metal mercaptans,such as alkali metal alkyl mercaptans, etc. In our co-pendingapplication Serial No. 134,460, filed April 1, 1 937, we describe andclaim various methods of producing para-nitro-phenyl thioethers and thethioethers so obtained. In our co-pending application Serial No.-98,828, filed August 31, 1936, we also describe methods of producingnitro-phenyl thioethers .and claim ortho-nitro-phenyl alkyl thioethers;the present application being a continuation-in-part of said priorapplication Ser. .No. 98,828.

Any of the nitro-phenyl alkyl. thioethers described in saidapplications. may be employed in the practice of the present invention.That is, in improving turbine oils by the present invention, we mayemploy thin-ethers having the following formula:

wherein X and ,2 represent hydrogen or a nitro group, at least one nitrogroup being present, and R represents an alkyl group.

Of this class of thioethers, the following specific thioethers may beused to advantage iriimprovingjurbine oils in accordance with thisinvention:

Methyl thioethers of para-nitrobenzene. Ethyl thioethers ofpara-nitrobenzene. Propyl thioethers of para-nitrobenzene'. n- Butylthioethers of para-nitrobenzene. n-Amyl thioethers of para-nitrobenzene.Iso-amyl thioethers of para.-nitrobenzene. Hexyl thioethers ofpara-nitrobenzene. Heptyl thioethers of para-nitrobenzene. Octylthioethers of para-nitrobenzene.

Nonyl thioethers of para-nitrobenzene. Decyl thioethers ofpara-nitrobenzene. Undecyl thioethers of para-nitrobenzene. Dodecylthioethers of para-nitrobenzene. Cetyl thioethers of para-nitrobenzene.Methyl thioethers of ortho-nitrobenzene. Ethyl thioethers ofortho-nitrobenzene. Propyl thioether-s of ortho-nitrobenzene. n-butylthioethers of ortho-nitrobenzene. n-amyl thioethers ofortho-nitrobenzene. Iso-amyl thioethersof ortho-nitrobenzene. Hexylthioethers or ortho-nitrobenzene. Heptyl thioethers ofortho-nitrobenzene. Octyl thioethers of ortho-nitrobenzene. Nonylthioethers of ortho-nitrobenzene. Decyl thioethers ofortho-nitrobenzene. Undecyl thioethers of ortho-nitrobenzene. Dodecylthioethers of ortho-nitrobenzene. 'Cetyl thioethers ofortho-nitrobenzene.

The butyl thioethers of 2:4-dinitro-benzene. The amyl thioethers of2:4-dinitro-benzene.

Also mixtures of these alkyl ethers may be employed in the practice ofthe present invention; for instance the mixed-amyl thioethers derivedfrom technical amyl mercapta'ns by methods described in the copendingapplications acknowledged ante. The para-nitro-phenyl alkyl thio- I Asstated, this invention may be practicedby introducing small amounts ofthese thioethers into the turbine oil while it is being re-cycled in theordinary manner. Also we may prepare improved turbine oils which arerelatively stable in storage, and which may be employed as makeup oilfor the turbine lubrication system.

In making such improved turbine oils, crdinarlly 0.1 to 1.0 per cent byweight on the oil of these thioethers is sumcient to produce the desiredimprovement of the turbine o'il. However in some cases larger amountsmay be employed; this being particularly so when the ortho nitrophenylalkyl thioethers are employed and it is desired also to impart extremepressure characteristics to theturbine oil. The particular proportionisemployed depend upon the particularthioethers and the turbine oilbeingcompounded together and the particular type of turbine lubricantdesired. Int-he practice of the present invention, any suitable turbineoil may be employed as the starting material. Into such oils we in- 7corporate these 'thioethers in any suitable man- '5 obtained. In theamounts here employed, the

ner. The thioether maybe dissolved in the oil by simply mixing thethioether. with the oil and agitating'the mixture until a uniformsolution is with ordinary turbine oil.

batches are excellent as make-up oil.

The ortho-nitro-phenyl I thioethers are readily and completely solublein turbine oils. In forming the improved lubricant, a slight warming ofthe oil mixture during the agitation facilitates obtaining uniformlubricants. Warming to temperatures between 100 F. and 180 F. is usuallysufllcient. Also the thioethers may be first dissolved in a part of theturbine oil to form a master batch, which is subsequently blended withadditional turbine oil to give the concentration of thioether desired ina particular turbine lubricating system. These master batchesareparticularly useful in improving the lubricant of a turbine, whichhas previously been operated- That is, these master These improvedturbine oils, when subjected show the improvements obtained as comparedwith the original turbine oil. In the inspection and examination ofturbine oils, in addition to the tests which are commonly applied to alllubricating oils, turbine oils are subjected to other tests. In certainof the standard tests of that oil, the emulsifying properties of theturbine oils are determined under various conditions. One of these testsis the steam emulsion test (ASTM D 157-36). In that test the time inseconds required for'the oil to separate from an equal volume ofcondensed steam is known as the SE number; a current of steam beingpassed into the turbine oil to form the oil and condensed steamemulsion. This test is an important one. It being important that theturbine oil retain its initial properties as long as possiblein use, theturbine oil is frequently subiected to special accelerated tests todetermine its resistance to deterioration. One such test is the specialoxidation test. In this test, 500 cc. of turbine oil is air blown at 212F. for, many hours; air being passed through the warm oil at the rate of10,000 cc. per hourfi The oxidized oil is then subjected to the steam"emulsion and other tests, to ascertain its stability with respect tocertain properties. When so tested, our improved-turbine oils aresuperior to the turbine oil from which they are prepared. By. varyingthe particular nitro-phenyl alkyl thioether used and the amount thereof,we can controllably improve one or more properties of the turbine oil.In this way, turbine oils having a specified set of properties can bereadily prepared by means of the present invention. In the illustrativeexamples given post, we set forth certain typical embodiments of thepresent invention. These examples are merely employed to improve turbineoils. In certain methods of refining mineral oils, particularly thelighter fractions thereof, such mercaptans are isolated from the oil.The so recovered mercaptans are complex mixtures, containing aliphatic,aromatic and cyclic compounds. These mercaptans, when converted intonitro-phenyl thioethers, yield ed thioethers containing such compounds.

In the general practice or this invention, we

find it'advantageous to employ thioethers or mixtures of thioetherswhich are liquid or easily liqueflable and which have the followingproperties: i

12.0 to 25.0 39.0 to .Below-55 to +32 to Neutralization No.--.' 0 to 0.1

For instance, the ethyl and my] thioethers of ortho-nitrobenzene areliquids having the properties set forth in Table 13; the ,amylthioethers being the -mixture of thioethers obtained from commercialamyl mercaptan.

TABLE B Ortho-nitro- Alkyl thio phenyl ethyl ether amyl Gravity: B6 21.015.1 Specific gravity: 60l60 F l. 1094 1. i162 Pounds per gallon 9. 749. 32 Viscosity, SUV: 100 40 l 43. 6 Pour: F Below -55 Below -55 Color:NPA I 6.5 6.0 Sulfur: Percent. 17.4 14.2 Neutralization N o Nil NilHowever, we may also employ the solid thioethers.

turbine oil to obtain a master batch which may be further diluted withmore oil to produce turbine oils having adjusted properties as desired.

The specific examples and tests given post are illustrative of detailembodiments of the present invention.

Example 1 Into a suitable vessel there are introduced 1000 gallons(approximately 7341 pounds) of a commercial turbine oil and the oil iswarmed to F. Then 18.35 pounds of the amyl thioether ofortho-nitrobenzel'ie, (0.25% by weight on the oil) is gradually addedand themixture agitated until a uniform blend is obtained; about onehour being required. In agitating the mixture, ordinary mechanicalagitators maybe employed or a current of air may be passed through thewarm mixture to produce uniform blending. The amyl thioether used inthis example had the properties given in Table A ante, and was a mixtureof isomeric amyl compounds, it being prepared from a commercial amyimercaptan and from commercial ortho-nitrochlorobenzene, both of whichare widely marketed in the chemical industries under those names.

a superior turbine oil.

Example 2 By the method of Example 1, a like amount of the amylthioethers of para-nitrobenzene is dissolved in'the turbine oil. Theturbine oil so obtained'is even superior to that produced in Example 1;the para-nitro substituted thioether 800 being an even betterimprovement agent for the turbine oil. The amyl thioether used in thisexample was also prepared for commercial met,-

captan, and likewise is a mixture of isomeric amyl thioethers. 1

Example 3 Another improved turbine oil is produced by the method ofExample 1 by employing the ethyl thioether of either ortho or para-nitrobenzene. In this embodiment, the ethyl thioether given in Table A may beemployed.

The properties of the improved oils obtained 5.5 to Dark I In usingthese thioethers, it is advantageous to first dissolve them in a part ofthe The mixture so obtained is 2,1 s4,4ss

'in Exampes 1 and 2, as compared with those of the original turbine oil,are as follows:

) TABLE C Improved oil Original 1 oil Example 1 Example 2 Gravity: API20.8 29.8 29.8 Sp. gr., 60l60 F 0. 8772 0. 8772 0.8772 Viscosity, SUV:

0. 826 0.826 390 390 450 450 0 0 1. 75 l. 76 Trace 0.01 NeutralizationNo Nil Nil Nil Steam emulsion test: ASTM.

D 157-36, SE No. sec l0 i2 11 From the above table it is clear that theaddition of the thioether does not materially change the generalcharacter of the turbine oil; but the utility of the oil as a lubricantfor turbines has been markedly improved. This improvement isdemonstratedwhen the original oil and the two improved oils aresubjected to the special oxidation test.

In the following Table D, tests made, after varying times of airblowing, with respect to neutralization number, SE number and colors aregiven. The effect of the nitro-phenyl alkyl thioethers in improving suchcharacteristics of the turbine oil are clear.

TABLE .D

Special oxidation test Diluted. I I

From the above table, it is evident that the compositions containing thepara-nitro-phenyl alkyl thioether have a very satisfactoryneutralization number and SE.number, even after 1800 hours in thespecial oxidation test.

After the original oil and improved oils had been subjected to thespecial oxidation test for g 1800 hours, the properties set forth inTable C "were again determined. In the following table,

the results of such determinations are set forth.

TABLE E Improved oils Original oil Example 1 Example 2 Gravity: API 29.729.7 29.6 Viscosity, SUV: 100 F 163 167 161 V-G constant 0. 825 0.826 0.827 Flash, F.. 395 400 395 Fire, 00: "F 455 460 455 Pour: F. +5. +5Color: NPA- 3.6 dil. 5.5 4 5 Carbon residue Peroent-. 0.05 0. 0.

store Med. hard Med. hard Med. hard Neutralization No 0. 22 0. 1 0 Steamemulsion test: ASTM D 157-36, SE No. (8136).. 448 461 254 From the abovetable, it is apparent that the nitro-phenyl alkyl thioethers not onlyimprove certain characteristicsof the oil but also do not deleteriously'affect other properties of the oil which were initially satisfactory.

In the above examples, other commercial 't'urbine oils may be employedand likewise improved. Also in lieu of the specific alkyl thioethersemployed, other thioethers may be used. Likewise the proportion ofthioethers employed might be varied as indicated ante in thisspecification. While we have illustrated our invention with reference tospecific examples, it will be understood that our invention is notlimited to the examples but may be practiced within the scope of theclaims hereinafter presented.

Moreover while we have in certain instances given certain ,preferredranges and proportions,

it will be understood that our hivention is not limited thereto, andthat such preferred; ranges and proportions are in general selected forparticular products and particular purposes; variations in proportionsand in the methods of preparation result in products of difierentcharacteristics, such products having individual advantages andutilities.

What we claim is:

1. As an improvement in' lubricating steam compensate for the oilcontained in the separated sludge and lace, the improvement whichcomprises introducing into said mineral lubricating ,.oil a minor amountof an alkyl thioether of nitrobenzene, and maintaining in said turbineoil during such recycling an amount of said thioether sufficient tosubstantiallyimprove the inbrication of the turbine" and the segregationof the oil from the sludge, sediment and lace. the

said alkyl thioether of nitrobenzene being intro-.

duced at one stage in said cycle and having the following formula:

wherein X and Y represent hydrogen-for 2. nitro group, at least onenitro group being present,

and n is 0 to 15.

2. The improved method of claim 1 wherein the amount of'said alkylthioether so introduced is sufficient to maintain between 0.1 and 1.0per cent by weight of said thioether dissolved in said turbine oil.

dissolved in said mineral lubricating oil.

' thioether is an 3. The improved method of claim 1 wherein saidthioether is an amyl thioether of ortho-nitrobenzene.

4. The improved method of claim 1 wherein said thioether is an amylthioether of para-ni- 5 trobenzene.

5. The improved method of claim 1 wherein said thioether is an amylthioether of 2:4-dinitrobenzene.

6. The improved method of claim 1 wherein said thioether is introducedinto the oil as it is being fed tothe turbine.

7. The improved method of claim 1 whereim the said thioether isintroduced during the collecting oi the turbine oil subsequent to itspassage through the turbine.

8. The improved method of claim 1 wherein the said thioether is addedwith the make-up oil in the form of a concentrated solution 01' saidthioether in the said make-up oil.

9. As an improved lubricant suitable for and capable of lubricatingsteam turbines, an improved turbine oil comprising a solution of a minoramount of an alkyl thioether of nitrobenzene dissolved in a major amountof a mineral lubricating oil capable of lubricating said turbines, thesaid alkyl thioether being present in an amount sufiicient tosubstantially improve the lubricating qualities, the stability and theresistance to emulsification of said oil and having the followingformula:

wherein X and Y represent hydrogen or a nitro group, at least. one nitrogroup being present,

andnis0to15. r i 10. The improved turbine oil, of claim 9,

wherein 0.1 to 1.0 per cent by weight on the oil of an amyl thioether oiortho-nitrobenzene is dissolvetrin said mineral lubricating oil.

11. The improved turbine oil 01 claim 9, wherein 0.1 to 1.0 per cent byweight on the oil of an amyl thioether of para-nitrobenz'ene isdissolved in said mineral lubricating oil.

12. The improved turbine oil of claim .9, wherein 0.1 to 1.0 per cnt byweight on the oil of an amyl thioether of '2:4'-dinitrobenzene is 13."As an improved composition for lubricating turbines,.the improvedlubricant comprising a major proportion of a mineral lubricating oilcapable oilubricatingturbines and a. minor proportion of an alkylthioether of nitrobenzene having the formula wherein X and Y represent asubstituent of the ela'ss consisting of hydrogen and-a nitro group, atleast one nitro group .being present, and R 3 represents an alwl group.v

14. The improvedlubricant'of claim 13 wherein said turbineoil fcontainsbetween 0.1 to 1.0 per cent by weight on the oil of said alkylthioether.

15. The composition of claim 13 whereinsaid thioether is an alkylthioether-of para-nitro- 16. The composition oi claim 13 wherein said valkyl thioether ot'2:4-dinitro4 benzene. TROY LEE Grimm.

. JAMES OTI-IO TURNER. rs

